Means for forging large shell rings e. g. for boiler shells

ABSTRACT

The forging of large shell rings, particularly for boilers, gives difficulty, but it is desirable to forge the rings in one piece. My invention provides apparatus suitable for forging such large rings, having a vertical mandrel which projects up the inside of the ring and a forging tool which works on the outside of the ring, against the counter-pressure of the mandrel. The forging tool has a generally vertical, arcuate forging surface and the forging tool executes a rocking movement during forging. The tool is driven by at least two hydraulic rams arranged one above the other, there being at least one pivotal connection between each ram and the forging tool.

United States Patent [151 3,695,079

Muller 51 Oct. 3, 1972 [54] MEANS FOR FORGING LARGE SHELL 1,996,181 4/1935 Wait ..72/ l l l RINGS E. G. FOR BOILER SHELLS 3,625,041 12/1971 Jeuken ..72/l ll [72] Inventor: rzgllgim 1813-1113;; Dusseldorf-Ger- Primary Examinerbowen A. Larson y Attorney-Holman & Stern [73] Assignee: Schloemann Aktiengesellschaft, Dusseldorf, Steinstrasse, Germany [57] ABSTRACT [22] Filed: May 28, 1971 The forging of large shell rings, particularly for boilers, gives difficulty, but it is desirable to forge the [21] Appl' l48079 rings in one piece. My invention provides apparatus suitable for forging such large rings, having a vertical [30] Foreign Application Pri rit Dat mandrel which projects up the inside of the ring and a forging tool which works on the outside of the ring, May 1970 Germany 20 26 6379 against the counter-pressure of the mandrel. The forging tool has a generally vertical, arcuate forging sur- U-S. Cl. face and the forging tool executes a rocking move- [5 hat. Cl. ment during forging. 'rhe tool is driven at least two Fleld of Search 74, hydraulic rams arranged one above the other there 398 being at least one pivotal connection between each ram and the forging tool. [56] References Cited 6 Claim, 2 Drawing Figures MEANS FOR FORGING LARGE SHELL RINGS E. G. FOR BOILER SHELLS This invention relates to apparatus for forging large shell rings, e.g., for boilers, including a stationary, generally vertical mandrel and a forging tool which can be moved relative thereto by means of a pressure fluid (e.g. hydraulic piston-and-cylinder) arrangement. In the case of apparatus described in the periodical Iron & Steel Engineering, Volume 40 (1963), No. 2, Pages 939/940, a horizontally reciprocating ram serves as a forging tool, which ram, in the case of large boiler shell rings, is disadvantageous because of the high pressing forces required. In addition, German published Specification Pat. No. 1,171,245, describes the forging of a flat workpiece with two forging beams symmetrically driven by means of a crank or eccentric drive, the beams having forging surfaces of arcuate curvature.

This invention is particularly concerned with forging shell rings having dimensions of say from 5 to meters diameter and an axial length of say about 4 meters, weighing say up to about 200 tons each, for the construction of large containers such as boilers. The forging should be effected in a press which must permit easy manipulation and enables one to work with relatively small press forces. The largest of the ring sizes mentioned above could not hitherto be produced with conventional presses because the clearances of the presses are too small. Hitherto such relatively large shell rings have generally been produced by welding together segments pre-bent to an arcuate curvature; flat plates are pre-bent on bending presses, wherein, for technical reasons, usually only the middle portion of the plate is given an arcuate curvature while the two ends remain flat and have to be removed after the bending. Furthermore the segments to be welded must have clean chamfers for the welding; with plate thicknesses of from 200 to 270 mm, for example, this preparation for welding requires a considerable amount of machining, and again involves loss of material. The welding itself, for example in the case of reactor containers, must be carried out with the utmost care, and with continual checking. The expenditure of time is considerable, since even modern welding machines apply only about 3 Kg. of welding material per hour to the container. Finally, many welded seams present difficult metallurgical problems, particularly when two welded seams abut upon one another. In comparison with the production of shell rings from segments, forged shell rings avoid most of the difficult and expensive welded seams.

The present invention provides apparatus for forging large shell rings including:

a stationary, generally vertical mandrel;

a forging tool (preferably in the form of a generally vertical beam) movable relative thereto, the forging tool having a generally vertical, arcuate forging surface facing the mandrel;

at least two pressure fluid devices arranged one above the other, for producing vertical rolling of the arcuate forging surface during forging; and

power-transmitting pivot means connecting the respective pressure fluid devices to the forging tool.

In operating the apparatus of the invention, the ring lies horizontally, and is continuously forged throughout its height. The indexing (rotating the ring) is preferably effected with indexing means including means for displacing the ring in a direction at an obtuse angle to the forging direction and simultaneously moving the inside of the ring away from the mandrel. When the forging tool is subsequently advanced, it produces an untwisting restoring torque (or moment) on the ring, which is internally supported eccentrically on the mandrel. When forging extremely heavy rings, which is possible using suitable designed apparatus according to the invention, the indexing means preferably includes means for applying a force to the ring to assist the centering, restoring moment applied to the ring by the mandrel and the forging tool when the tool is advanced such assisting means may be in the form of an auxiliary pressure fluid ram; the assisting means may also be used when the material of the ring is still soft.

It is conceivable to support the forging tool (which would have a forging surface in the form of an arc of a circle) for pivoting about the center of curvature of the arc, the center being movable up and down. However, a more advantageous and space-saving arrangement is as follows. In order to make the forging movement possible, and to take up the shortening of the vertical distance between the two points of application of the pressure fluid devices on the forging tool from one another (which occurs when the two points of application are not vertical one above the other), the devices may be rockably supported. It is necessary, however, that there should be respective power-transmitting pivot means between the piston rods (which move strictly in straight lines) of the pressure fluid devices and the forging tool, since the forging tool, on account of the great pressure on the ring, cannot slip up and down. In a preferred arrangement however, the pressure fluid devices are fixed and there are respective articulated links pivoted to the forging tool and to the piston rods of the pressure fluid devices.

In order to take up bending moments during forging, the device preferably further comprises a bearer extending generally parallel to the mandrel, said pressure fluid devices being mounted on the bearer, and means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring.

The invention will be further described, by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a side view of forging apparatus in ac cordance with the invention; and

FIG. 2 is a plan view of the apparatus, showing indexing means for indexing a ring during a forging operation.

In the apparatus of FIG. 1, a vertical, circular crosssection mandrel 2 projects through a horizontal boiler shell ring 1 which is to be forged; the mandrel 2 forms one limb of a U-shaped structure having a lower connecting bearer 3. An upright forging tool in the form of a forging beam 4 has its lower end pivoted to a sliding shoe 5 which slides on the connecting bearer 3 and can be removed by lifting it vertically upwards. The forging beam 4 has a forging surface 6 in the shape of an arc of a circle, which presses the ring 1 against the mandrel 2.

The second limb of the U-shaped structure is a bearer 7, on which are fixed, one above the other, two horizontal piston-and-cylinder ram devices 8 and 9.

Each of the piston rods of the ram devices 8, 9 moves rectilinearly and is pivotally connected, by means of a power-transmitting hinged bearing 10, to an intermediate rod 11, which in its turn is pivotally connected by means of a power-transmitting hinged bearing 12 to the forging beam 4.

The upper ends of the bearer 7 and of the mandrel 2 are held together by means of a strut 13 which is pivoted to the bearer 7 and engages a spigot 2a on the mandrel. The ram devices 8 and 9 are operated hydraulically, the admission pipes for the forging stroke and for the return stroke leading by way of controlling devices 14 and 15 respectively to a source 16 of hydraulic pressure.

The admission and discharge of hydraulic medium into and out of the cylinders of the ram devices 8 and 9 are so controlled that the curved forging surface 6 of the forging beam 4 produces a vertical surface on the ring 1. The advancing piston must here execute a decelerating movement, in which it proceeds, when forging in an upward direction, at first comparatively quickly and then more slowly. The rate of discharge of hydraulic medium from the other cylinder is exactly the same as the rate of supply of hydraulic medium to the cylinder of the advancing piston. For any radius of curvature of the forging surface of the forging beam there is always a predetermined, unchanging program for the controlling devices 14 and 15. The amounts of flow are adjusted during the forging stroke; adjustment is possible because each forging stroke lasts several seconds.

FIG. 2 shows an indexing device for the ring 1 which is located between the mandrel 2 and the forging beam 4. The indexing device has hydraulic transporting means (shown as a ram 17) by means of which the ring 1 is displaceable at an obtuse angle to the direction of forging; this angle is at least more than 90. Opposite to the hydraulic transporting ram 17 is provided an auxiliary cylinder 18, which is co-axial with the hydraulic transporting ram 17 and presses its plunger piston against the ring 1. The subsequent centering, restoring moment which is applied to the ring 1 by'means of the mandrel 2 and the moving forging beam 4 is reinforced (assisted) by the force produced by the auxiliary cylinder 18.

To index the ring 1, the forging beam 4 is first of all retracted by means of the two ram devices 8 and 9. Then the hydraulic transporting ram 17 pushes the ring so that its inner side is moved away from the mandrel 2. Then the ring 1 is pushed against the mandrel 2 by the forging beam (which is initially inclined towards the right with respect to the ring 1 in FIG. 2), and clamped, the transporting ram 17 being meanwhile withdrawn.

The centering, restoring moment thus arising is reinforced by the auxiliary cylinder until the ring 1 is again symmetrically located. Thereupon a forging deformation is effected.

I claim:

1. Apparatus for forging large shell rings comprising:

a stationary, generally vertical mandrel;

a forging tool movable relative thereto, the forging tool having a generally vertical, arcuate forging surface facing the mandrel;

at least two pressure fluid devices arranged one above the other, for producing vertical rolling of the arcuate forging surface during forging; and power-transmitting pivot means connecting the respective pressure fluid devices to the forging tool.

2. Apparatus as claimed in claim 1, and further comprising means for indexing the ring, the indexing means comprising means for displacing the ring in a direction at an obtuse angle to the forging direction and silmutaneously moving the inside of the ring away from the mandrel.

3. Apparatus as claimed in claim 2, wherein the indexing means further comprises means for applying a force to the ring to assist the centering, restoring moment applied to the ring by the mandrel and the forging tool when the tool is advanced.

4. Apparatus as claimed in claim 1, and further comprising:

a bearer extending generally parallel to the mandrel,

said pressure fluid devices being mounted on the bearer; and

means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring.

5. Apparatus as claimed in claim 2, and further comprising:

a bearer extending generally parallel to the mandrel,

said pressure fluid devices being mounted on the bearer; and

means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring.

6. Apparatus as claimed in claim 3, and further comprising:

a bearer extending generally parallel to the mandrel,

said pressure fluid devices being mounted on the bearer; and

means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring. 

1. Apparatus for forging large shell rings comprising: a stationary, generally vertical mandrel; a forging tool movable relative thereto, the forging tool having a generally vertical, arcuate forging surface facing the mandrel; at least two pressure fluid devices arranged one above the other, for producing vertical rolling of the arcuate forging surface during forging; and power-transmitting pivot means connecting the respective pressure fluid devices to the forging tool.
 2. Apparatus as claimed in claim 1, and further comprising means for indexing the ring, the indexing means comprising means for displacing the ring in a direction at an obtuse angle to the forging direction and silmutaneously moving the inside of the ring away from the mandrel.
 3. Apparatus as claimed in claim 2, wherein the indexing means further comprises means for applying a force to the ring to assist the centering, restoring moment applied to the ring by the mandrel and the forging tool when the tool is advanced.
 4. Apparatus as claimed in claim 1, and further comprising: a bearer extending generally parallel to the mandrel, said pressure fluid devices being mounted on the bearer; and means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring.
 5. Apparatus as claimed in claim 2, and further comprising: a bearer extending generally parallel to the mandrel, said pressure fluid devices being mounted on the bearer; and means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring.
 6. Apparatus as claimed in claim 3, and further comprising: a bearer extending generally parallel to the mandrel, said pressure fluid devices being mounted on the bearer; and means interconnecting the bearer and the mandrel to form a frame which can be opened for insertion or removal of the shell ring. 